41 votes 41 votes A CPU has $24$-$bit$ instructions. A program starts at address $300$ (in decimal). Which one of the following is a legal program counter (all values in decimal)? $400$ $500$ $600$ $700$ CO and Architecture gatecse-2006 co-and-architecture machine-instruction easy isro2009 + – Rucha Shelke asked Sep 16, 2014 • edited Jun 20, 2018 by Milicevic3306 Rucha Shelke 16.1k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
2 votes 2 votes After each instruction cycle the PC needs to be updated to point to the next instruction in memory. INSTRUCTION SIZE : 24BITS or 3Bytes Address of next instruction : 303 then 306 and so on. So it is an AP series and only 600 comes under this series. So answer is C akshat sinha answered Apr 19, 2018 akshat sinha comment Share Follow See all 0 reply Please log in or register to add a comment.
2 votes 2 votes Actually the question is incomplete. It should be mentioned in the question that the CPU is byte-addressible so that the PC will increment byte by byte. Now because the instruction is 3byte, the PC has to increment 3 times. So the answer is 600, since it is the only option which is multiple of 3. shubhk answered Oct 3, 2018 shubhk comment Share Follow See all 0 reply Please log in or register to add a comment.
1 votes 1 votes Each instruction is 24 bits ..so we need three cells it means that 1 cell consists of 8 bits so I1: 300 -302 I2: 303-305 I3:306-308 . . . . continue like this so we can see here PC has a multiplicative of 3. So 600 is the answer. focus _GATE answered Oct 5, 2015 • edited Sep 30, 2023 by Hira Thakur focus _GATE comment Share Follow See all 0 reply Please log in or register to add a comment.
1 votes 1 votes When nothing is given, we always have to assume byte addressability. So, 1 instruction = 3 B. From mem location 300, load 99 instructions. We'll be on mem location 597, and PC would point to 600. Or simply, look for multiples of 3. Option C JashanArora answered Aug 26, 2019 JashanArora comment Share Follow See all 0 reply Please log in or register to add a comment.